Move May Help Chairman Masayoshi Son Build Case for Merger With T-Mobile US

SAN ANTONIO—Sprint Corp. said it will help rural carriers get access to the phones and airwaves they need to offer high-speed wireless service, a move that could help Chairman Masayoshi Son win allies as he builds the case for a merger with T-Mobile US Inc.

Rural wireless carriers have lagged behind their larger counterparts in building out the fastest network technology, known as LTE, in part because the smaller companies didn't have...